The objective of this proposal is to characterize the transmission of the putative AIDS agent (HTLV III) in the sexual partners and children of Haitian AIDS patients and to determine the natural history of the infection in the affected family members. We will determine the prevalence of HTLV III seropositivity, and seroconversion rates in the sexual partners and children. We will compare and contrast the AIDs families with similar studies of age-sex matched friends of the AIDS sexual partner. The children of these friends will serve as controls for the children of the AIDS families. HTLV III seropositive subjects (children and adults) will be followed for periods of 1-4 years to determine the natural history of this infection. Evidence for vertical and horizontal infection within families will be sought. HTLV III viral isolation studies of pregnant women and young children will assist in this determination. We will examine sexual and non-sexual activities of the study subjects to determine if particular activities are associated with acquisition of HTLV III infection or influence the natural history of the infection.